Form for vulcanizable plastic articles.



APPLICATION FILED MAR. 2. 915.

Patented Dec. 26,1916.

(lb-tonne MYROM n. CLARK, or nns'rmes-uro'n-nunson, new roan, nssien'on E30 nosiron nunnnn snon con rary, A conrone'rron or nassacnnenrrs.

3 none: roe viineemzaisnn rtnsric narrows.

Specification of Letters Patent. Patemtgfl B 2% 3916,

Application filed March 2, 1915. filerial lio. 11,801.

To all whom it m ay concern Be it known that I, Mrnox .H. CLARK, a

, Articles, of which the following is a full,

clear, and exact description.

My inventionvrelates to improvements in forms for use in connection with the vulcanization of articles made from rubber, rubber-like, or similar materials and 'fiber.

It is customary in the manufacture of articles of this character to form the article on the outside of a rigid support or form and subject the outer surface of the article to pressure which is resisted by the form, while allowing the escape of entrapped air, gases,'and otherdeleterious fluids, from the interior of the article by maintaining portions of said article beneath its outer sur- .face in communication with the interior of the form in which a vacuum may be maintained. Usually this process is carried out during vulcanization of the article so that the article is vulcanized in the required shape simultaneously with the removal of the entrapped air and the like. In place of the vacuum, pressure is often employed upon the interior of the article, said interior pressure being met by a greater pressure upon the ei-rteriez' of the article. In either case it is essential that the condition of the article being treated shall be, as to its pressure condition, at all times under the control of the operator. During this controlled differential pressure cure, it has hitherto been difficult to maintain an accurate differential of pressure due. to leakage through the wall of the formresulting ina partial equalization of the pressure. a p

The objectof my invention, therefore, is to so treat the form that leakage through its wall will be positively prevented, and this I accomplish, preferably by producing an impervious coating upon the wall of the form which completely seals the wall of the form, as will be hereinafter more fully described. I

One apparatus for carrying the invention into effect is illustrated in the accompanying drawing in which: Figure 1 is a sect-ional view through a form for a boot embodying my improvements; Fig. :2 is a fragmentary VlW showing the modification;

Fig. 3 is a. fragmentary View showing another modification.

Referring to the drawing, 10 designates a support or form upon which. the article is built, in this case a boot form is shown, the

same being hollow and having a-plurality' of orifices 11 inits wall which expose the boot 12, during cure, to the difierentia'l of pressure above described. The form is provided. j

with a closure 13 making the interior air tight.

A pipel le'ads'intothe interior of i the form whereby the interior may be brought into communication with a suction" pump or pressure pump (not shown), there being afluid regulating deit ice'lli operatively connected with the pipe to vary the pressure within the form. i

The form may be made of any desired rigid material, but is preferably made of aluminum, which on account of its strength and light weight is particularly advantageous. However, there exists a certain porosity in aluminum which renders its use somewhat impractical for this purpose, but this is also true of wood and even other metals besides aluminum to a more or less extent. Therefore to fit the form, whether made of wood, metal, or other desired material, for use in connection with the difierential pressure curing of vulcanizable articles, 1 preferably apply to the wall of the form an impervious coating 16 which seals the pores of the material from which the form is made and positively prevents leale age through the wall of the form.

Any desired coating material, which will seal the pores of the particular material from which the form is made, may be used, and I have found the varnish known as Japan to be particularly suited for use in connection with aluminum forms.

I contemplate also the use of a sealing material which, contrary to being applied merely as a superficial coating may be impregnated or worked into the somewhat cellulous structure of wood, metal, or other material from which the form is made.

In the drawing I have illustrated various positions of the impervious coating upon the form, such as for instance in Fig. 1, the coating is shown as covering the entire 'interioiface of the form: in Fig. 2. the coat ing is shown confined merely to the exposed outer face of the form beyond the boot; and

in Figfi 'lh coating is shown as confined to the inner faceof the form beyond that portion vof the form occupied by the boot.

a Id( not limit myself to any particular allocation of the coating shown,'since I contemplate. localizing'or even-generally applying the coating, or even impregnating the.

' material from which the form itself is made,

. without restriction as to area or other diip' mensions, it being simply necessary to the practice of my invention that all or any of the pores of any material from which the.

form is made be sealed against leakage uh- I der the influence of a differential pressure internal and. external pressure upon the 7:

form may be accurately controlled.

( A-hollow metallic form for supporting i a vulcanizable plastic article during a differential pressure cure, means for exposing 80 the interior of the form to a lesserlpressure than the exterior'of the form, and an im-- pervious coating, sealing and preventing leakage through the pores of the form so that the internal and external pressure upon 35 the form may be accurately controlled.

3. A hollow form for supporting a vulcanizable plastic article having a passage Way affording. communication between the interior and exterior of the form Within the 40 area adapted to be covered'by the article, and a superficial coating forthe form to enhance its'imperviousness. i

4. .A hollow form for supporting a vul- 'c'anizable plastic article having a passage 4 way alfording' communication between the interior and exterior of the form within the area adapted to be covered by the article,

and a coating upon the interior of the form to enhance its imperviousness. 50 Signed at New York, this 26th day of Feb., 1915. MYRON H. CLARK; WVitnesses MAUDE PFAFFMAN'N, CLARENCE GUILD, Jr. 

